My favorite (and very accurate) conversion site is www.convert-me.com Click on "cooking" on left hand side. Use the empty box to type your ingredient and choose from the drop down menu. Some items may not be listed (ie: not all types of extracts are listed, but you can use vanilla as the "ingredient" choice, or water to get your measurement for something like coconut extract). Then enter your measurement into the right category and hit ENTER. It converts it into a number of different "measurements". I love this site!

If you are in the US or another jurisdiction that requires the inclusion of nutrition information on food labels, stated both in metric and non-metric amounts (which could include a number of counted items, for ingredients like dates), the most reliable conversion method is to calculate based on the values on the label.

So, for example, if the package says that a serving of dates is “2 dates (46 grams)”, you can do simple arithmetic to figure out how many dates will have the mass — number of grams — called for in the recipe. ;o)